1. Field of the Invention
This invention relates to a linear displacement transducer.
2. Description of the Prior Art
A linear displacement transducer including a hybrid coil formed of a primary coil and two secondary coils is already known. The two secondary coils connected in series and in opposition are arranged at least partially facing the primary coil. A coupling core moves in both directions between the primary and secondary coils so as to cause voltages to vary continuously at the terminals of the transformer's secondary coils.
In this type of known transducer, the two secondary coils are connected in series and in opposition, and when these two coils are identical the voltage is cancelled out when the coupling core is placed symmetrically in relation to the secondary coils. When the core moves in either direction, the amplitude of the voltage increases linearly, but the phase at the secondary terminals is displaced by a 180.degree. angle depending on the direction of the core. In certain cases of measurement, this phase displacement is ignored, with only the variation in voltage amplitude as a function of the core displacement being of interest. Introduction of an additional secondary coil, which is placed between the two preceding coils, makes it possible to displace the placement of the core according to the length of this additional coil, whereby the voltage of the secondary terminals is cancelled out. This amounts to adding a constant voltage, in relation to the preceding case, proportional to the voltage of the primary.
In the transducer described above, the amplitude of the voltage at the terminals of the secondary coils depends on the voltage delivered by the primary. When this voltage varies around a given position, fluctuations in amplitude occur in the voltage supplied by the secondary coils.